Common mode filter, signal passing module and method of manufacturing common mode filter

ABSTRACT

Disclosed herein is a common mode filter including: at least four coil layers having a primary coil and a secondary coil; and discontinuous parts each connecting starting points of each of the primary coil and the secondary coil positioned on the lowest layer among the coil layer to ending points of each of the primary coil and the secondary coil positioned on the highest layer among the coil layers with each other in series. The common mode filter is able to be miniaturized and to improve impedance characteristics.

CROSS REFERENCE(S) TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. Section 119 ofKorean Patent Application Serial No. 10-2014-0052485 entitled “CommonMode Filter, Signal Passing Module and Method of Manufacturing CommonMode Filter” filed on Apr. 30, 2014, which is hereby incorporated byreference in its entirety into this application.

BACKGROUND OF THE INVENTION

1. Technical Field

The present disclosure relates to a common mode filter.

2. Description of the Related Art

A common mode filter is an electronic component that has been widelyused in order to remove common mode noise in various electronic devices.

In accordance with the recent trend toward miniaturization, slimness,and multi-functionalization of electronic components, research has beenconducted toward a common mode filter capable of being miniaturized andthinned simultaneously with improving noise removing performance.

SUMMARY OF THE INVENTION

An object of the present invention is to miniaturize a common modefilter and improve impedance characteristics.

Objects of the present invention are not limited to the above-mentionedobjects. That is, other objects that are not mentioned may be obviouslyunderstood by those skilled in the art to which the present inventionpertains from the following description.

According to an exemplary embodiment of the present invention, there isprovided a common mode filter having four coil layers or more includinga primary coil and a secondary coil, a size of the common mode filter aybe reduced and impedance characteristics may be improved.

The primary coil of the common mode filter may be connected in seriesfrom a starting point thereof to an ending point thereof and thesecondary coil of the common mode filter may be connected in series froma starting point thereof to an ending point thereof.

Each of the primary coil and the secondary coil of the respective coillayers may be connected to each of the primary coil and the secondarycoil of other coil layer through an internal terminal and an externalterminal.

A discontinuous part made of an insulating material may be providedbetween one coil layer and external terminals provided on a coil layerof an upper portion thereof to allow each of the primary coil and thesecondary coil to be connected with each other in series from the lowestlayer to the highest layer.

Meanwhile, the common mode filter may further include an externalelectrode or an external plating terminal, a value of existence of thediscontinuous part should not be forgotten. That is, the externalterminals positioned on both surfaces of the discontinuous part need notto be electrically conducted by the external plating terminal.

According to another exemplary embodiment of the present invention,there is provided a signal passing module including the common modefilter as described above provided between a first terminal and a secondterminal.

According to another exemplary embodiment of the present invention,there is provided a method of manufacturing a common mode filter capableof manufacturing the common mode filter.

A layer including the discontinuous part as described above may bereferred to as a function layer, and the function layer may be formedbetween a third coil layer and a fourth coil layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view schematically showing a common mode filteraccording to an exemplary embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line I-I′ of FIG. 1;

FIG. 3A is a cross-sectional view taken along line II-IP of FIG. 1;

FIG. 3B is a cross-sectional view taken along the line III-III′ of FIG.1;

FIG. 3C is a cross-sectional view taken along the line IV-PP of FIG. 1;

FIG. 4A is a plan view schematically illustrating a first coil layer ofthe common mode filter according to the exemplary embodiment of thepresent invention;

FIG. 4B is a plan view schematically illustrating a second coil layer ofthe common mode filter according to the exemplary embodiment of thepresent invention;

FIG. 4C is a plan view schematically illustrating a third coil layer ofthe common mode filter according to the exemplary embodiment of thepresent invention;

FIG. 4D is a plan view schematically illustrating a fourth coil layer ofthe common mode filter according to the exemplary embodiment of thepresent invention;

FIG. 5 is a view schematically illustrating a connection relationshipbetween primary coils according to an exemplary embodiment of thepresent invention;

FIG. 6 is a perspective view schematically illustrating a common modefilter according to another exemplary embodiment of the presentinvention;

FIG. 7 is a cross-sectional view taken along line I-I′ of FIG. 6;

FIG. 8 is a block diagram schematically illustrating a signal passingmodule according to an exemplary embodiment of the present invention;

FIG. 9 is a circuit diagram schematically illustrating a common modefilter according to an exemplary embodiment of the present invention;

FIGS. 10A to 10E illustrate a method of manufacturing a common modefilter according to an exemplary embodiment of the present invention,where:

FIG. 10A is a cross-sectional view schematically illustrating a processof forming a first coil layer with respect to a cross-section takenalong line I-I′ of FIG. 1;

FIG. 10B is a cross-sectional view schematically illustrating a processof forming a second coil layer with respect to a cross-section takenalong line I-I′ of FIG. 1;

FIG. 10C is a cross-sectional view schematically illustrating a processof forming a third coil layer with respect to a cross-section takenalong line I-I′ of FIG. 1;

FIG. 10D is a cross-sectional view schematically illustrating a processof forming a fourth coil layer with respect to a cross-section takenalong line I-I′ of FIG. 1;

FIG. 10E is a cross-sectional view schematically illustrating a processof forming a fourth coil layer with respect to a cross-section takenalong line III-III′ of FIG. 1;

FIGS. 11A to 11I are plan views of the respective masks which are usedin a method of manufacturing a common mode filter according to anexemplary embodiment of the present invention, where:

FIG. 11A is a plan view of a mask for a first layer;

FIG. 11B is a plan view of a mask for a second layer;

FIG. 11C is a plan view of a mask for a third layer;

FIG. 11D is a plan view of a mask for a fourth layer;

FIG. 11E is a plan view of a first mask;

FIG. 11F is a plan view of a second mask;

FIG. 11G is a plan view of a third mask;

FIG. 11H is a plan view of a state in which the third mask of FIG. 11Gis rotated counterclockwise by 90°;

FIG. 11I is a plan view of a state in which the mask for the fourthlayer of FIG. 11D is rotated counterclockwise by 90°;

FIG. 12 is a cross-sectional view schematically illustrating across-section which is obtained by cutting the common mode filteraccording to another exemplary embodiment of the present invention alongline I-I′ of FIG. 1;

FIG. 13A is a cross-sectional view schematically illustrating across-section which is obtained by cutting the common mode filteraccording to another exemplary embodiment of the present invention alongline II-II′ of FIG. 1;

FIG. 13B is a cross-sectional view schematically illustrating across-section which is obtained by cutting a common mode filteraccording to still another exemplary embodiment of the present inventionalong line II-II′ of FIG. 1;

FIG. 14A is a plan view schematically illustrating a (2N−1)-th coillayer of the common mode filter according to another exemplaryembodiment of the present invention;

FIG. 14B is a plan view schematically illustrating a 2N-th coil layer ofthe common mode filter according to another exemplary embodiment of thepresent invention;

FIG. 14C is a plan view schematically illustrating a 2N-th coil layer ofthe common mode filter according to still another exemplary embodimentof the present invention; and

FIG. 15 is a view schematically illustrating a connection relationshipbetween primary coils according to another exemplary embodiment of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various advantages and features of the present invention and methodsaccomplishing thereof will become apparent from the followingdescription of exemplary embodiments with reference to the accompanyingdrawings. However, the present invention may be modified in manydifferent forms and it should not be limited to exemplary embodimentsset forth herein. These exemplary embodiments may be provided so thatthis disclosure will be thorough and complete, and will fully convey thescope of the invention to those skilled in the art. Meanwhile, likereference numerals throughout the specification denote like elements.

Terms used in the present specification are for explaining exemplaryembodiments rather than limiting the present invention. Unlessexplicitly described to the contrary, a singular form includes a pluralform in the present specification. The words ‘comprise’ and/or‘comprising’, and the like will be understood to imply the inclusion ofstated constituents, steps, operations and/or elements but not theexclusion of any other constituents, steps, operations and/or elements.

For purpose of simplification and clearness of illustration, a generalconfiguration scheme will be shown in the accompanying drawings, and adetailed description of the feature and the technology which are wellknown in the art will be omitted. Additionally, components shown in theaccompanying drawings are not necessarily shown to scale. For example,sizes of some components shown in the accompanying drawings may beexaggerated as compared with other components in order to assist inunderstanding of exemplary embodiments of the present invention. Likereference numerals on different drawings will denote like components,and similar reference numerals on different drawings will denote similarcomponents, but are not necessarily limited thereto.

In the specification and the claims, terms such as “first”, “second”,“third”, “fourth”, and the like, if any, will be used to distinguishsimilar components from each other and be used to describe a specificsequence or a generation sequence, but is not necessarily limitedthereto. For example, it may be understood that these terms arecompatible with each other under an appropriate environment so thatexemplary embodiments of the present invention to be described below maybe operated in a sequence different from a sequence shown or describedherein. Likewise, in the present specification, in the case in which itis described that a method includes a series of steps, a sequence ofthese steps suggested herein is not necessarily a sequence in whichthese steps may be executed. That is, any described step may be omittedor any other step that is not described herein may be added to themethod.

In the specification and the claims, terms such as “left”, “right”,“front”, “rear”, “top, “bottom”, “over”, “under”, and the like, if any,do not necessarily indicate relative positions that are not changed, butare used for description. It may be understood that these terms arecompatible with each other under an appropriate environment so thatexemplary embodiments of the present invention to be described below maybe operated in a direction different from a direction shown or describedherein. A term “connected” used herein is defined as being directly orindirectly connected in an electrical or non-electrical scheme. Targetsdescribed as being “adjacent to” each other may physically contact eachother, be close to each other, or be in the same general range orregion, in the context in which the above phrase is used. Here, a phrase“in an exemplary embodiment” means the same exemplary embodiment, but isnot necessarily limited thereto.

Hereinafter, a configuration and an acting effect of exemplaryembodiments of the present invention will be described in more detailwith reference to the accompanying drawings.

FIG. 1 is a perspective view schematically showing a common mode filter100 according to an exemplary embodiment of the present invention, FIG.2 is a cross-sectional view taken along line I-I′ of FIG. 1, FIG. 3A isa cross-sectional view taken along line II-IP of FIG. 1, FIG. 3B is across-sectional view taken along the line III-III′ of FIG. 1, and FIG.3C is a cross-sectional view taken along the line IV-IV′ of FIG. 1.

In addition, FIG. 4A is a plan view schematically illustrating a firstcoil layer L1 of the common mode filter 100 according to the exemplaryembodiment of the present invention, FIG. 4B is a plan viewschematically illustrating a second coil layer L2 of the common modefilter 100 according to the exemplary embodiment of the presentinvention, FIG. 4C is a plan view schematically illustrating a thirdcoil layer L3 of the common mode filter 100 according to the exemplaryembodiment of the present invention, and FIG. 4D is a plan viewschematically illustrating a fourth coil layer L4 of the common modefilter 100 according to the exemplary embodiment of the presentinvention.

In addition, FIG. 5 is a view schematically illustrating a connectionrelationship between primary coils PC according to an exemplaryembodiment of the present invention.

Referring to FIGS. 1 to 5, the common mode filter 100 according to theexemplary embodiment of the present invention may include four coillayers L1, L2, L3 and L4 including primary coils PC and secondary coilsSC. Here, a component including the four coil layer L1, L2, L3 and L4may be referred to as a coil part 120.

In addition to the four coil layers, the common mode filter 100 mayinclude a substrate 110 made of a magnetic material such as ferrite orthe like, a magnetic body part 130, an insulating part 122, externalelectrodes 141, 142, 143 and 144, an external plating terminal 150, andthe like.

Here, a scheme in which the primary coil PC and the secondary coil SCare formed in a spiral shape on the same planar surface may be referredto as a simultaneous coil scheme. This simultaneous coil scheme isdifferent from a so-called single coil scheme in which the primary coiland the second coil are formed to be included in different layers fromeach other.

In this case, when predetermined impedance characteristics isimplemented by forming the coil on the same area using a conducivepattern having the same line width, the common mode filter of thesimultaneous coil scheme may be implemented by the number of layerssmaller than the common mode filter of the single coil scheme.

For example, in the case in which an impedance of 30 to 35Ω isimplemented by the common mode filter having an area of 0.4 mm×0.3 mm,when the simultaneous coil scheme is used, the impedance may beimplemented by two coil layers, while when the single coil scheme isused, four coil layers may be required.

Meanwhile, the existing common mode filter of the simultaneous coilscheme has been generally implemented in a form including two coillayers or less.

However, in order to improve the impedance characteristics whileperforming miniaturization, the common mode filter 100 according to theexemplary embodiment of the present invention may include four coillayers or more including the primary coil PC and the secondary coil SC.

In this case, the primary coil and the secondary coil included in eachof the coil layers need not to directly contact with the primary coiland the secondary coil formed on the other layer. To this end, theinsulating part 122 may be provided between the conductive patterns. Inaddition, the primary coil and the secondary coil included in each ofthe coil layers may be connected to the primary coils included in othercoil layers through internal terminals and external terminals.

Planar shapes of the first coil layer L1 to the fourth coil layer L4 maybe understood with reference to FIGS. 4A to 4D.

For example, according to an exemplary embodiment of the presentinvention, a first primary coil PC1 and a first secondary coil SC1 maybe formed together in a spiral shape on the first coil layer L1 in astate in which they are spaced apart from each other by a predetermineddistance, a first primary external terminal P1 may be connected to oneend of the first primary coil PC1, and a first primary internal terminalPI1 may be connected to the other end of the first primary coil PC1.Similarly, a first secondary external terminal S1 may be connected toone end of the first secondary coil SC1 and a first secondary internalterminal SI1 may be connected to the other end of the first secondarycoil SC1.

Meanwhile, the second coil layer L2 to the fourth coil layer L4 may alsobe implemented in the form similar to that as described above.

Here, referring to FIG. 5, according to an exemplary embodiment of thepresent invention, it may be understood that the primary coil may beconnected in series from a starting point thereof to an ending pointthereof, since the first primary external terminal P1, the first primarycoil PC1, the first secondary internal terminal SI1, a first primary viaPV1, a second primary internal terminal PI2, a second primary coil PC2,a second primary external terminal P2, a third primary external terminalP3, a third primary coil PC3, a third primary internal terminal P13, asecond primary via PV2, a fourth primary internal terminal PI4, a fourthprimary coil PC4, and the fourth primary external terminal P4 aresequentially connected in the above-mentioned order.

Of course, although not shown, the secondary coil may also be connectedin series by the same manner. That is, it may be understood that thesecondary coil may be connected in series from a starting point thereofto an ending point thereof, since the first secondary external terminalS1, the first secondary coil SC1, the first secondary internal terminalSI1, a first secondary via SV1, a second secondary internal terminalSI2, a second secondary coil SC2, a second secondary external terminalS2, a third secondary external terminal S3, a third secondary coil SC3,a third secondary internal terminal S13, a second secondary via SV2, afourth secondary internal terminal SI4, a fourth secondary coil SC4, andthe fourth secondary external terminal S4 are sequentially connected inthe above-mentioned order.

Meanwhile, FIG. 8 is a block diagram schematically illustrating a signalpassing module 1000 according to an exemplary embodiment of the presentinvention and FIG. 9 is a circuit diagram schematically illustrating acommon mode filter 100 according to an exemplary embodiment of thepresent invention.

Referring to FIG. 8, the signal passing module 1000 according to theexemplary embodiment of the present invention may include a firstterminal 200, a common mode filter 100, and a second terminal 300.Various filters 400 such as an LC filter, and the like may be furtherprovided between the common mode filter 100 and the second terminal 300,if necessary.

The signal passing module 1000 mentioned above may be provided in afirst electronic device ED to serve to transmit and receive signals toand from another external device, for example, a second electronicdevice illustrated in FIG. 8.

Here, if it is assumed that the first electronic device ED and thesecond electronic device transmits and receives a differential modesignal to transmit and receive predetermined data to and from eachother, a common mode signal which is interposed during the signaltransmission and reception process may be considered as noise, and thecommon mode filter 100 may serve to reduce the common mode noise asdescribed above.

First, the first terminal 200 may be selectively connected or blocked toor from the second electronic device.

In addition, the common mode filter 100 as described above or to bedescribed below may be connected to the first terminal 200.

In addition, the second terminal 300 may be directly connected to thecommon mode filter 100 or connected to the common mode filter 100 via afilter 400 to serve to output a signal in which at least a portion ofthe common mode noise is removed.

Referring to FIG. 9, in the common mode filter 100 according to theexemplary embodiment of the present invention, the starting point of theprimary coil PC may be the first primary external terminal P1 and theending point of the primary coil PC may be the fourth primary externalterminal P4. In addition, the starting point of the secondary coil SCmay be the first secondary external terminal S1 and the ending point ofthe secondary coil SC may be the fourth secondary external terminal S4.

As such, only if both ends of the primary coil and both ends of thesecondary coil are each provided with the terminals, the common modefilter 100 may be connected onto a signal transmission and receptionpath to perform a function of removing the common mode noise.

In addition, referring to FIGS. 1 to 3D, according to an exemplaryembodiment of the present invention, the first primary external terminalP1 may be connected to a first primary external electrode 141, thefourth primary external terminal P4 may be connected to a second primaryexternal electrode 142, the first secondary external terminal S1 may beconnected to a first secondary externally electrode 143, and the fourthsecondary external terminal S4 may be connected to a second secondaryexternal electrode 144. Further, the first primary external electrode141 may be connected to a first primary external plating terminal 151,the second primary external electrode 142 may be connected to a secondprimary external plating terminal 152, the first secondary externalelectrode 143 may be connected to a first secondary external platingterminal 153, and the second secondary external electrode 144 may beconnected to the second secondary external plating terminal 154. As aresult, the first primary external plating terminal 151 may be connectedto the first primary external terminal P1, the second primary externalplating terminal 152 may be fourth primary external terminal P4, thefirst secondary external plating terminal 153 may be connected to thefirst secondary external terminal S1, and the second secondary externalplating terminal 154 may be connected to the fourth primary externalterminal P4.

Accordingly, the first primary external electrode 141 or the firstprimary external plating terminal 151 may be connected to the firstterminal 200, and the first secondary external electrode 143 or thefirst secondary external plating terminal 153 may be connected to thefirst terminal 200.

In addition, the second primary external electrode 142 or the secondprimary external plating terminal 152 may be connected to the secondterminal 300, and the second secondary external electrode 144 or thesecond secondary external plating terminal 154 may be connected to thesecond terminal 300.

Meanwhile, referring to FIGS. 4A to 5, in the common mode filter 100according to an exemplary embodiment of the present invention, the firstprimary external terminal P1 and the second primary external terminal P2are provided to a position at which they are not overlapped with eachother in a vertical projection region, while the second primary externalterminal P2, the third primary external terminal P3 and the fourthprimary external terminal P4 are provided to a position at which theyare overlapped with one another in the vertical projection region. As aresult, the common mode filter 100 as illustrated in FIG. 9 may beimplemented.

Here, referring to FIG. 5, it may be understood that the second primaryexternal terminal P2 and the third primary external terminal P3 aredirectly connected to each other, while the third primary externalterminal P3 and the fourth primary external terminal P4 need not to bedirectly connected to each other.

As described above, since the second primary external terminal P2, thethird primary external terminal P3, and the fourth primary externalterminal P4 are provided to the position at which they are overlappedwith each other in the vertical projection region, the second primaryexternal terminal P2 and the third primary external terminal P3 may bedirectly connected to each other. However, since the third primaryexternal terminal P3 and the fourth primary external terminal P4 neednot to be directly connected to each other while being overlapped witheach other in the vertical projection region, a separate unit may berequired. In the common mode filter 100 according to the exemplaryembodiment of the present invention, as the separate unit, a firstdiscontinuous part DC1 made of an insulating material may be providedbetween the third primary external terminal P3 and the fourth primaryexternal terminal P4.

Although the view such as FIG. 5 is not separately shown with respect tothe secondary coil, the secondary coil may include a seconddiscontinuous part DC2 according to a principle similar to the case ofthe first discontinuous part DC1 of the primary coil as set forth.

Referring to FIGS. 1 and 4D, the common mode filter 100 according to theexemplary embodiment of the present invention may further include theexternal electrodes 141, 142, 143 and 143 and the external platingterminal 150.

The external electrodes may be provided on the fourth coil layer L4.That is, the second primary external electrode 142 contacting an uppersurface of the fourth primary external terminal P4 and the secondsecondary external electrode 144 contacting an upper surface of thefourth secondary external terminal S4 may be provided.

Meanwhile, the first primary external electrode 141 may be provided onthe first primary external terminal P1 and the first secondary externalelectrode 143 may be provided on the first secondary external terminalS1. However, the first primary external electrode 141 and the firstprimary external terminal P1 are not directly in contact with eachother, the first secondary external electrode 143 and the firstsecondary external terminal S1 are not directly in contact with eachother. Accordingly, in the vertical projection region of the firstprimary external terminal P1, the second coil layer L2 may be furtherprovided with a second dummy primary external terminal DP2, the thirdcoil layer L3 may be further provided with a third dummy primaryexternal terminal DP3, and the fourth coil layer L4 may be furtherprovided with a fourth dummy primary external terminal DP4. In addition,in the vertical projection region of the first secondary externalterminal S1, the second coil layer L2 may be further provided with asecond dummy secondary external terminal DS2, the third coil layer L3may be further provided with a third dummy secondary external terminalDS3, and the fourth coil layer L4 may be further provided with a fourthdummy secondary external terminal DS4. In this case, the term Each ofthe first primary external terminal P1 and the first secondary externalterminal S1 provided to the first coil layer L1 may be connected to eachof the first primary external electrode 141 and the second primaryexternal electrode 142 through the dummy terminals as described above.

In addition, the external plating terminal 150 may be provided onsurfaces of the external electrodes 141, 142, 143 and 144, and may serveto improve efficiency of work in which the common mode filter 100 ismounted on a circuit board (not shown) of the electronic device, or thelike and to improve adhesion between the common mode filter 100 and thecircuit board (not shown). In addition, the external plating terminal150 may be implemented using typical nickel or a nickel alloy.

Meanwhile, the external plating terminal 150 may be formed on an uppersurface of the external electrode as well as a side thereof. However, ithas been described in the common mode filter 100 according to theexemplary embodiment of the present invention that the firstdiscontinuous part DC1 may be provided to a vertically downward regionof the second primary external electrode 142, and the seconddiscontinuous part DC2 may be provided to a vertically downward regionof the second secondary external electrode 144. The first discontinuouspart DC1 and the second discontinuous part DC2 may perform a functionallowing each of the primary coil and the secondary coil to be connectedin series from the starting point to the ending point. Accordingly, atleast the second primary external plating terminal 152 contacting thesecond primary external electrode 142 and the second secondary externalplating terminal 154 contacting the second secondary external electrode144 need not to be directly in contact with the external terminalsprovided to downward regions of at least the first discontinuous partDC1 and the second discontinuous part DC2. That is, the second primaryexternal plating terminal 152 contacting the second primary externalelectrode 142 need not to be directly in contact with the third primaryexternal terminal P3 and the second primary external terminal P2, andthe second primary external plating terminal 152 contacting the secondprimary external electrode 142 need not to be directly in contact withthe third secondary external terminal S3 and the second secondaryexternal terminal S2. To this end, a first insulating wall IW1 formed ofan insulating material may be provided at least between the thirdprimary external terminal P3 and the second primary external terminalP2, and the second primary external plating terminal 152. In addition, asecond insulating wall IW2 formed of an insulating material may beprovided at least between the third secondary external terminal S3 andthe second secondary external terminal S2, and the second secondaryexternal plating terminal 154.

FIG. 6 is a perspective view schematically illustrating a common modefilter 100′ according to another exemplary embodiment of the presentinvention and FIG. 7 is a cross-sectional view taken along line I-I′ ofFIG. 6.

Referring to FIGS. 6 and 7, it may be understood that the same objectmay be implemented without having the first insulating wall IW1 and thesecond insulating wall IW2 as describe above by providing a secondprimary external plating terminal 152′ and a second secondary externalplating terminal 154′ to only on an upper surface of the common modefiler 100.

FIGS. 10A to 10E illustrate a method of manufacturing a common modefilter 100 according to an exemplary embodiment of the presentinvention, where: FIG. 10A is a cross-sectional view schematicallyillustrating a process of forming a first coil layer L1 with respect toa cross-section taken along line I-I′ of FIG. 1, FIG. 10B is across-sectional view schematically illustrating a process of forming asecond coil layer L2 with respect to a cross-section taken along lineI-I′ of FIG. 1, FIG. 10C is a cross-sectional view schematicallyillustrating a process of forming a third coil layer L3 with respect toa cross-section taken along line I-I′ of FIG. 1, FIG. 10D is across-sectional view schematically illustrating a process of forming afourth coil layer L4 with respect to a cross-section taken along lineI-I′ of FIG. 1, and FIG. 10E is a cross-sectional view schematicallyillustrating a process of forming a fourth coil layer L4 with respect toa cross-section taken along line III-III′ of FIG. 1.

FIGS. 11A to 11I are plan views of the respective masks which are usedin a method of manufacturing a common mode filter 100 according to anexemplary embodiment of the present invention, where: FIG. 11A is a planview of a mask for a first layer ML1, FIG. 11B is a plan view of a maskfor a second layer ML2, FIG. 11C is a plan view of a mask for a thirdlayer ML3, FIG. 11D is a plan view of a mask for a fourth layer ML4,FIG. 11E is a plan view of a first mask M1, FIG. 11F is a plan view of asecond mask M2, FIG. 11G is a plan view of a third mask M3, FIG. 11H isa plan view of a state in which the third mask M3 of FIG. 11G is rotatedcounterclockwise by 90°, and FIG. 11I is a plan view of a state in whichthe mask for the fourth layer ML4 of FIG. 11D is rotatedcounterclockwise by 90°.

Meanwhile, although the present specification describes the respectiveprocesses based on a lithography method of a negative scheme, it may beunderstood that the common mode filter may be manufactured by alithography method or a laminate method of a positive scheme.

In addition, since FIGS. 10A to 10D are the cross-sectional views forthe cross-section taken along line I-I′ of FIG. 1 and FIG. 10E is theprocess cross-sectional view for the cross-section taken along lineIII-III′ of FIG. 1, portions which are not visible from thecross-section taken along line I-I′ and the cross-section taken alongline III-III′ are not indicated. However, referring to FIGS. 1 to 11Itogether, processes of performing the method of manufacturing the commonmode filter according to the exemplary embodiment of the presentinvention may be sufficiently understood.

Referring to FIGS. 10A to 11I together with FIGS. 1 to 9, the method ofmanufacturing the common mode filter 100 according to the exemplaryembodiment of the present invention may include forming first coil layerL1 to fourth coil layer L4.

In this case, the first coil layer L1 may be formed on a substrate 110made of a magnetic material such as ferrite, or the like.

First, referring to FIG. 10A, a seed layer SE may be formed on an uppersurface of the substrate 110 and a photoresist PR may be formed on anupper surface of the seed layer SE. Next, an exposure process isperformed using the mask for the first layer ML1 and the photoresist PRin the exposed region may be then removed. In this case, the mask forthe first layer ML1 may be a mask formed to allow light to penetratethrough a portion corresponding to a region which will be provided withthe first primary coil PC1, the second secondary coil SC2, the firstprimary internal terminal PI1, the first primary external terminal P1,the first secondary internal terminal SI1, and the second secondaryexternal terminal S2 which configure the first coil layer L1 asdescribed above, and one example of the mask for the first layer ML1 isillustrated in FIG. 11A.

Next, a plating process may be performed on a region in which thephotoresist PR is removed, and the photoresist PR and the seed layer SEof portions except for regions having the first dummy primary externalterminal DP1, the first dummy secondary external terminal DS1, and thelike formed thereon may be then removed. As a result, the first coillayer L1 having a planar shape as illustrated in FIG. 4A may be formed.

Referring to FIG. 10B, in a state in which the photoresist PR is formedon the upper surface of the first coil layer L1, the exposure processmay be performed using the first mask M1 and the photoresist PR in theexposed region may be then removed. In this case, one example of thefirst mask M1 is illustrated in FIG. 11E, and the first mask M1 may beformed to allow the light to penetrate through a position correspondingto each of the four external terminals or dummy external terminals andpositions corresponding to the primary via and the secondary via.

Next, the seed layer SE may be formed on regions in which thephotoresist PR exposed by the first mask M1 is removed and an upperregion of the remaining photoresist PR.

Next, in a state in which the photoresist PR covering an upper portionof the seed layer SE is formed, an exposure process is performed usingthe mask for the second layer ML2 and the photoresist PR in the exposedregion may be then removed.

Next, a plating process may be performed on a region in which thephotoresist PR is removed, and the photoresist PR and the seed layer SEof portions except for regions having the second primary externalterminal P2, the second secondary coil SC2, the second secondaryexternal terminal S2, and the like formed thereon may be then removed.As a result, the second coil layer L2 having a planar shape asillustrated in FIG. 4B may be formed.

Referring to FIG. 10C, in a state in which the photoresist PR is formedon the second coil layer L2, the exposure process may be performed usingthe second mask M2 and the photoresist PR in the exposed region may bethen removed. In this case, the second mask M2 may be formed to allowthe light to penetrate through a position corresponding to each of thefour external terminals or dummy external terminals, similar to thefirst mask M1 used in the process of forming the second coil layer L2.However, there is a difference in that the first mask M1 is formed so asto allow the light to penetrate through the regions corresponding to theprimary via and the secondary via, but the second mask M2 is formed soas not to allow the light to penetrate through the regions correspondingto the primary via and the secondary via, and one example of the secondmask M2 is illustrated in FIG. 11F.

Next, the seed layer SE may be formed on regions in which thephotoresist PR exposed by the second mask M2 is removed and an upperregion of the remaining photoresist PR.

Next, in a state in which the photoresist PR covering an upper portionof the seed layer SE is formed, an exposure process is performed usingthe mask for the third layer ML3 and the photoresist PR in the exposedregion may be then removed.

Next, a plating process may be performed on a region in which thephotoresist PR is removed, and the photoresist PR and the seed layer SEof portions except for regions having the third primary externalterminal P3, the third primary coil PC3, the third secondary externalterminal S3, and the like formed thereon may be then removed. As aresult, the third coil layer L3 having a planar shape as illustrated inFIG. 4C may be formed.

Referring to FIGS. 10D and 10E, in a state in which the photoresist PRis formed on the upper surface of the third coil layer L3, the exposureprocess may be performed using the third mask M3 and the photoresist PRin the exposed region may be then removed. In this case, unlike the firsmask M1, the third mask M3 is formed so as not to allow the light topenetrate through the position corresponding to each of the thirdprimary external terminal P3 and the third secondary external terminalS3 and is formed so as to allow the light to penetrate through only theposition corresponding to each of the third primary dummy externalterminal and the third secondary dummy external terminal and theposition corresponding to each of the primary via and the secondary via,and one example of the third mask M3 is illustrated in FIGS. 11G and11H.

Next, the seed layer SE may be formed on regions in which thephotoresist PR exposed by the third mask M3 is removed and an upperregion of the remaining photoresist PR.

Next, in a state in which the photoresist PR covering an upper portionof the seed layer SE is formed, an exposure process is performed usingthe mask for the fourth layer ML4 and the photoresist PR in the exposedregion may be then removed.

Next, a plating process may be performed on a region in which thephotoresist PR is removed, and the photoresist PR and the seed layer SEof portions except for regions having the fourth primary externalterminal P4, the fourth secondary coil SC4, the fourth secondaryexternal terminal S4, the fourth dummy secondary external terminal DS4,and the like formed thereon may be then removed. As a result, the fourthcoil layer L4 having a planar shape as illustrated in FIG. 4D may beformed.

Here, referring to FIGS. 10D and 10E, the photoresist PR remains betweenthe third primary external terminal P3 and the fourth primary externalterminal P4 and between the third secondary external terminal S3 and thefourth secondary external terminal S4 to thereby prevent the externalterminals from being directly in contact with each other. These portionscorrespond to the first discontinuous part DC1 and the seconddiscontinuous part DC2 described above with reference to FIGS. 1 to 4D.That is, although FIGS. 1 to 4D indicate a different kind of hatchingfrom the insulating part 122 in order to allow the first discontinuouspart DC1 and the second discontinuous part DC2 to be clearly understood,it may be appreciated that the first discontinuous part DC1 and thesecond discontinuous part DC2 may be implemented together with theinsulating part 122 by the photoresist PR. Meanwhile, a layer includingthe first discontinuous part DC1 and the second discontinuous part DC2may be separately referred to as a function layer L4′. That is, thefunction layer L4′ may be provided between the third coil layer L3 andthe fourth coil layer L4, and may mean a layer preventing the thirdprimary external terminal P3 and the fourth primary external terminal P4from being directly in contact with each other and preventing the thirdsecondary external terminal S3 and the fourth secondary externalterminal S4 from being directly in contact with each other, and allowingthe third dummy primary external terminal DP3 and the fourth dummyprimary external terminal DP4 to be directly in contact with each otherand allowing the third dummy secondary external terminal DS3 and thefourth dummy secondary external terminal DS4 to be directly in contactwith each other.

In addition, although FIGS. 10A to 10E have explicitly indicated theseed layer SE to assist in understanding for the process, FIGS. 2 to 3Chave indicated the seed layer SE without being classified for purpose ofsimplification of the drawings.

In addition, although FIG. 3A, and the like illustrate a case in whichthe primary coil and the secondary coil in each coil layer are alignedin a vertical direction, coil patterns in an upper layer and a lowerlayer may be provided to be alternated with each other, thereby reducingparasitic capacitance between coils in the upper layer and the lowerlayer.

Meanwhile, although not shown, after the fourth coil layer L4 is formed,a process of forming the external electrodes on the fourth coil layerL4, a process of forming the magnetic body part 130, a process offorming the external plating terminal, and the like may be furtherperformed. Referring to FIGS. 1 to 11I together, the process ofmanufacturing the above-mentioned components may be sufficientlyunderstood.

FIG. 12 is a cross-sectional view schematically illustrating across-section which is obtained by cutting the common mode filteraccording to another exemplary embodiment of the present invention alongline I-I′ of FIG. 1, FIG. 13A is a cross-sectional view schematicallyillustrating a cross-section which is obtained by cutting the commonmode filter according to another exemplary embodiment of the presentinvention along line II-IP of FIG. 1, FIG. 13B is a cross-sectional viewschematically illustrating a cross-section which is obtained by cuttinga common mode filter according to still another exemplary embodiment ofthe present invention along line II-II′ of FIG. 1, FIG. 14A is a planview schematically illustrating a (2N−1)-th coil layer of the commonmode filter according to another exemplary embodiment of the presentinvention, FIG. 14B is a plan view schematically illustrating a 2N-thcoil layer of the common mode filter according to another exemplaryembodiment of the present invention, FIG. 14C is a plan viewschematically illustrating a 2N-th coil layer of the common mode filteraccording to still another exemplary embodiment of the presentinvention, and FIG. 15 is a view schematically illustrating a connectionrelationship between primary coils according to another exemplaryembodiment of the present invention.

Referring to FIGS. 12 to 15 together with FIGS. 1 to 11I as describedabove, it may be appreciated that the common mode filter according tothe exemplary embodiment of the present invention may have the coillayer formed of more layers such as six layers, eight layers, or thelike.

FIG. 12, or the like illustrates the four or more coil layers as a(2N−1)-th coil layer L2N−1 and a 2N-th coil layer L2N, where N is anatural number of 3 or more. That is, if N is 3, the common mode filter200 according to the exemplary embodiment of the present invention mayinclude first through sixth coil layers. In addition, if N is 4, thecommon mode filter 200 according to the exemplary embodiment of thepresent invention may include first through eighth coil layers.

However, only two layers of the highest portion among the four or morecoil layers are shown for purpose of simplification of illustration.Although not shown, it may be appreciated that if N is the naturalnumber of 4 or more, a (2N−2)-th coil layer, a (2N−3)-th coil layer, andthe like may be further provided below the (2N−1)-th coil layer L2N−1.

Meanwhile, a (2N−1)-th primary coil PC2N−1 and a (2N−1)-th secondarycoil SC2N−1 may be formed together in a spiral shape on the (2N−1)-thcoil layer in a state in which they are spaced apart from each other bya predetermined distance, a (2N−1)-th primary external terminal P2N−1may be connected to one end of the (2N−1)-th primary coil PC2N−1, and a(2N−1)-th primary internal terminal PI2N−1 may be connected to the otherend of the (2N−1)-th primary coil PC2N−1. Similarly, a (2N−1)-thsecondary external terminal S2N−1 may be connected to one end of the(2N−1)-th secondary coil SC2N−1 and a (2N−1)-th secondary internalterminal SI2N−1 may be connected to the other end of the (2N−1)-thsecondary coil SC2N−1.

In addition, a 2N-th coil layer L2N may also be implemented in the formsimilar to that as described above.

However, if the fifth coil layer to the 2N-th coil layer are furtherprovided on the fourth coil layer, discontinuous parts DC2N−1 and DC2Nneed to be provided between the fifth coil layer and the sixth coillayer, and between the (2N−1)-th coil layer L2N−1 and the 2N-th coillayer L2N, respectively.

Here, it was described above with reference to FIG. 5 that the firstprimary external terminal P1 to the fourth primary external terminal P4are sequentially connected. Further, referring to FIG. 15, it may beunderstood that the primary coil may be connected in series from astarting point thereof to an ending point thereof, since the (2N−1)-thprimary external terminal P2N−1, the (2N−1)-th primary coil PC2N−1, the(2N−1) primary internal terminal PI2N−1, an N-th primary via PVN, a2N-th primary internal terminal PI2N, a 2N-th primary coil PC2N, and a2N-th primary external terminal P2N are sequentially connected in theabove-mentioned order.

In this case, the (2N−1)-th discontinuous part may be provided to aregion between the (2N−1)-th primary external terminal P2N−1 and the2N-th primary external terminal P2N.

Although not shown, the secondary coil may also be connected in seriesby the same manner. That is, it may be understood that the secondarycoil may be connected in series from a starting point thereof to anending point thereof by sequentially connecting a (2N−1)-th secondaryexternal terminal S2N−1, a (2N−1)-th secondary coil SC2N−1, a (2N−1)-thsecondary internal terminal SI2N−1, an N-th secondary via SVN, a 2N-thsecondary internal terminal, a 2N-th secondary coil SC2N, and a 2N-thsecondary external terminal S2N in the above-mentioned order.

In this case, the 2N-th discontinuous part may be provided to a regionbetween the (2N−1)-th secondary external terminal S2N−1 and the 2N-thsecondary external terminal S2N.

FIG. 14C illustrates a planar shape of a 2N-th coil layer of the commonmode filter according to still another exemplary embodiment of thepresent invention.

In the common mode filter according to the exemplary embodiment of thepresent invention, the 2N-th primary internal terminal PI2N and the2N-th primary external terminal P2N of the 2N-th coil layer may beconnected to each other by a primary lead pattern PL, which is shorterthan a spiral coil, instead of the primary coil formed in a spiralshape. The 2N-th secondary internal terminal SI2N and the 2N-thsecondary external terminal S2N may be connected to each other by asecondary lead pattern SL, which is shorter than the spiral coil,instead of the secondary coil.

Although the exemplary embodiment of the present inventionillustratively describes a case in which the primary lead pattern PL andthe secondary lead pattern SL are provided on the 2N-th coil layer, theprimary lead pattern and the secondary lead pattern may be provided oneven-numbered layers such as the second coil layer, the fourth coillayer, and the like, instead of the primary coil or the secondary coil,if necessary.

An overlapped description for the similar matters as described abovewill be omitted.

According to the exemplary embodiment of the present invention, thecommon mode filter may be miniaturized and the impedance characteristicsmay be improved.

What is claimed is:
 1. A common mode filter comprising: at least fourcoil layers having a primary coil and a secondary coil; anddiscontinuous parts, each connecting starting points of each of theprimary coil and the secondary coil positioned on the lowest layer amongthe coil layers and ending points of each of the primary coil and thesecondary coil positioned on the highest layer among the coil layerswith each other in series.
 2. The common mode filter according to claim1, wherein the primary coil and the secondary coil provided on each ofthe at least four coil layers are provided in a spiral shape on the sameplan surface to be spaced apart from each other by a preset distance. 3.The common mode filter according to claim 2, wherein each of the primarycoils and secondary coils of the at least four coil layers includes aninternal terminal and an external terminal at one end and the other end.4. The common mode filter according to claim 3, wherein each of theexternal terminals of the at least four coil layers is overlapped witheach of external terminals positioned over or under thereof in avertical direction region, and the discontinuous part is provided onlybetween the external terminal of one coil layer among the at least fourcoil layers and an external terminal positioned thereunder, and each ofexternal terminals of the remaining coil layers contacts each ofexternal terminals positioned over or under thereof.
 5. The common modefilter according to claim 3, wherein each of the external terminals ofthe at least four coil layers is overlapped with each of externalterminals positioned over or under thereof in a vertical directionregion, and each of the external terminals contacts each of externalterminals positioned over or under thereof, and only one coil layeramong the at least four coil layers has the discontinuous part providedbetween the external terminal of the coil layer and an external terminalpositioned on an upper portion thereof.
 6. The common mode filteraccording to claim 1, wherein the discontinuous part is made of aninsulating material.
 7. The common mode filter according to claim 1,wherein 2N coil layers are provided and the discontinuous parts are eachprovided on over all odd-numbered layers of three layers or more, Nbeing a natural number of 3 or more.
 8. A common mode filter comprising:a first primary external electrode and a second primary externalelectrode connected with each other in series through at least four coillayers; and a first secondary external electrode and a second secondaryexternal electrode connected with each other in series through the atleast four coil layers.
 9. The common mode filter according to claim 8,further comprising: first primary external terminals provided on each ofthe at least four coil layers and having at least a portion thereofpositioned under the first primary external electrode; and secondprimary external terminals provided on each of the at least four coillayers and having at least a portion thereof positioned in a verticaldownward region of the second primary external electrode, whereinregions between the first primary external terminals are provided with aconductive material, and only one region among regions between thesecond primary external terminals is provided with a first discontinuouspart made of an insulating material and the remaining regions areprovided with the conductive material.
 10. The common mode filteraccording to claim 9, further comprising: first secondary externalterminals provided on each of the coil layers and having at least aportion thereof positioned under the first secondary external electrode;and second secondary external terminals provided on each of the at leastfour coil layers and having at least a portion thereof positioned underthe second secondary external electrode, wherein regions between thefirst secondary external terminals are provided with the conductivematerial, and only one region among regions between the second secondaryexternal terminals is provided with a second discontinuous part made ofthe insulating material and the remaining regions are provided with theconductive material.
 11. The common mode filter according to claim 10,further comprising an external plating terminal contacting an outersurface of at least one of the first primary external electrode, thesecond primary external electrode, the first secondary externalelectrode, and the second secondary external electrode.
 12. The commonmode filter according to claim 11, wherein the external plating terminalincludes: a first primary external plating terminal contacting at leastportion of the outer surface of the first primary external electrode; asecond primary external plating terminal contacting at least portion ofthe outer surface of the second primary external electrode; a firstsecondary external plating terminal contacting at least portion of theouter surface of the first secondary external electrode; and a secondsecondary external plating terminal contacting at least portion of theouter surface of the second secondary external electrode.
 13. The commonmode filter according to claim 12, wherein the primary externalterminals having at least a portion positioned under the firstdiscontinuous part and the second primary external plating terminal arenot directly in contact with each other, and the primary externalterminals having at least a portion positioned under the seconddiscontinuous part and the second secondary external plating terminalare not directly in contact with each other.
 14. The common mode filteraccording to claim 12, wherein a first insulating wall made of theinsulating material is provided between the second primary externalterminals and the second primary external plating terminal, and a secondinsulating wall made of the insulating material is provided between thesecond secondary external terminals and the second secondary externalplating terminal.
 15. A signal passing module provided in a firstelectronic device to perform a signal transmission and reception betweena second electronic device and the first electronic device, the signalpassing module comprising: a first terminal having the second electronicdevice selectively connected or blocked thereto or therefrom; a commonmode filter of claim 8 connected to the first terminal; and a secondterminal outputting a signal in which at least portion of common modenoise is removed by the common mode filter.
 16. The signal passingmodule according to claim 15, wherein the first primary externalelectrode and the first secondary external electrode are connected tothe first terminal, and the second primary external electrode and thesecond secondary external electrode are connected to the secondterminal.
 17. The signal passing module according to claim 16, whereinthe common mode filter and the second terminal further have a filterprovided therebetween.
 18. A common mode filter comprising: a first coillayer having a first primary coil and a first secondary coil provided ina spiral shape on a single plane surface to be spaced apart from eachother by a preset distance; a first primary external terminal formed onthe first coil layer and provided to one end of the first primary coil;a first primary internal terminal formed on the first coil layer andprovided to the other end of the first primary coil; a first secondaryexternal terminal formed on the first coil layer and provided to one endof the first secondary coil; a first secondary internal terminal formedon the first coil layer and provided to the other end of the firstsecondary coil; a second coil layer having a second primary coil and asecond secondary coil provided in a spiral shape on a single planesurface to be spaced apart from each other by a preset distance; asecond primary external terminal formed on the second coil layer andprovided to one end of the second primary coil; a second primaryinternal terminal formed on the second coil layer and provided to theother end of the second primary coil; a second secondary externalterminal formed on the second coil layer and provided to one end of thesecond secondary coil; a second secondary internal terminal formed onthe second coil layer and provided to the other end of the secondsecondary coil; a third coil layer having a third primary coil and athird secondary coil provided in a spiral shape on a single planesurface to be spaced apart from each other by a preset distance; a thirdprimary external terminal formed on the third coil layer and provided toone end of the third primary coil; a third primary internal terminalformed on the third coil layer and provided to the other end of thethird primary coil; a third secondary external terminal formed on thethird coil layer and provided to one end of the third secondary coil; athird secondary internal terminal formed on the third coil layer andprovided to the other end of the third secondary coil; a fourth coillayer having a fourth primary coil and a fourth secondary coil providedin a spiral shape on a single plane surface to be spaced apart from eachother by a preset distance; a fourth primary external terminal formed onthe fourth coil layer and provided to one end of the fourth primarycoil; a fourth primary internal terminal formed on the fourth coil layerand provided to the other end of the fourth primary coil; a fourthsecondary external terminal formed on the fourth coil layer and providedto one end of the fourth secondary coil; and a fourth secondary internalterminal formed on the fourth coil layer and provided to the other endof the fourth secondary coil, wherein the first coil layer, the secondcoil layer, the third coil layer, and the fourth coil layer aresequentially stacked, the first primary internal terminal is in contactwith the second primary internal terminal directly or through a via, thesecond primary external terminal is in contact with the third primaryexternal terminal directly or through a via, the third primary internalterminal is in contact with the fourth primary internal terminaldirectly or through a via, and a first discontinuous part made of aninsulting material is provided between the third primary externalterminal and the fourth primary external terminal.
 19. The common modefilter according to claim 18, wherein the first secondary internalterminal is in contact with the second secondary internal terminaldirectly or through a via, the second secondary external terminal is incontact with the third secondary external terminal directly or through avia, the third secondary internal terminal is in contact with the fourthsecondary internal terminal directly or through a via, and a seconddiscontinuous part made of an insulting material is provided between thethird secondary external terminal and the fourth secondary externalterminal.
 20. The common mode filter according to claim 19, furthercomprising: a first primary external electrode provided on the firstprimary external terminal; a second primary external electrode providedon the fourth primary external terminal; a first secondary externalelectrode provided on the first secondary external terminal; and asecond secondary external electrode provided on the fourth secondaryexternal terminal.
 21. The common mode filter according to claim 20,further comprising: a first primary external plating terminal contactingat least portion of an outer surface of the first primary externalelectrode; a second primary external plating terminal contacting atleast portion of an outer surface of the second primary externalelectrode; a first secondary external plating terminal contacting atleast portion of an outer surface of the first secondary externalelectrode; and a second secondary external plating terminal contactingat least portion of an outer surface of the second secondary externalelectrode.
 22. The common mode filter according to claim 21, wherein thesecond primary external plating terminal is not directly in contact withthe third primary external terminal, and the second secondary externalplating terminal is not directly in contact with the third secondaryexternal terminal.
 23. The common mode filter according to claim 21,wherein the second primary external plating terminal is in contact withonly the second primary external electrode through a conductivematerial, and the second secondary external plating terminal is incontact with only the second secondary external electrode through aconductive material.
 24. The common mode filter according to claim 23,further comprising: a first insulating wall provided between the secondprimary external plating terminal and the third primary externalterminal and made of an insulating material; and a second insulatingwall provided between the second secondary external plating terminal andthe third secondary external terminal and made of an insulatingmaterial.
 25. A method of manufacturing a common mode filter having atleast four coil layers including a primary coil and a secondary coil,the method comprising: forming a discontinuous part connecting startingpoints of each of the primary coil and the secondary coil positioned onthe lowest layer among the at least four coil layers and ending pointsof each of the primary coil and the secondary coil positioned on thehighest layer among the coil layers with each other in series.
 26. Themethod according to claim 25, wherein the at least four coil layersinclude a first coil layer, a second coil layer, a third coil layer, anda fourth coil layer, and the discontinuous part is provided in afunction layer formed between the third coil layer and the fourth coillayer.
 27. A method of manufacturing a common mode filter, the methodcomprising: forming a first coil layer including a first primary coilhaving one end connected to a first primary external terminal and theother end connected to a first primary internal terminal and a firstsecondary coil having one end connected to a first secondary externalterminal and the other end connected to a first secondary internalterminal; forming, on the first coil layer, a second coil layerincluding a second primary coil having one end connected to a secondprimary external terminal and the other end connected to a secondprimary internal terminal and a second secondary coil having one endconnected to a second secondary external terminal and the other endconnected to a second secondary internal terminal; forming, on thesecond coil layer, a third coil layer including a third primary coilhaving one end connected to a third primary external terminal and theother end connected to a third primary internal terminal and a thirdsecondary coil having one end connected to a third secondary externalterminal and the other end connected to a third secondary internalterminal; and forming, on the third coil layer, a fourth coil layerincluding a fourth primary coil having one end connected to a fourthprimary external terminal and the other end connected to a fourthprimary internal terminal and a fourth secondary coil having one endconnected to a fourth secondary external terminal and the other endconnected to a fourth secondary internal terminal, wherein a firstdiscontinuous part made of an insulting material is provided between anupper surface of the third primary external terminal and a lower surfaceof the fourth primary external terminal, and a second discontinuous partmade of an insulting material is provided between an upper surface ofthe third secondary external terminal and a lower surface of the fourthsecondary external terminal.
 28. The method according to claim 27,further comprising: forming a primary external electrode on an uppersurface of the fourth primary external terminal and forming a secondaryexternal electrode on an upper surface of the fourth secondary externalterminal.
 29. The method according to claim 28, further comprising:forming a primary external plating terminal contacting at least portionof an outer surface of the primary external electrode and forming asecondary external plating terminal contacting at least portion of anouter surface of the secondary external electrode.
 30. The methodaccording to claim 29, wherein the primary external plating terminal isformed not to be directly in contact with the second primary externalterminal and the third primary external terminal, and the secondaryexternal plating terminal is formed not to be directly in contact withthe second secondary external terminal and the third secondary externalterminal.
 31. A common mode filter comprising: an insulation part; andat least four coil layers sequentially stacked in the insulation part,each having a primary coil and a secondary coil, the primary coil andthe secondary coil having a spiral shape, and being spaced apart fromeach other, wherein the primary coils of the at least four coil layersare connected in series and the secondary coils of the at least fourcoil layers are connected in series.
 32. The common mode filter of claim31, further comprising: a substrate on which the insulation part isdisposed; a magnetic body part disposed on the substrate and theinsulation part; a first primary external electrode and a second primaryexternal electrode being connected via the primary coils of the at leastfour coil layers; and a first secondary external electrode and a secondprimary external electrode being connected via the secondary coils ofthe at least four coil layers, wherein the first and second primaryexternal electrodes and the first and second secondary externalelectrodes are disposed on four corners of the at least four coillayers.
 33. The common mode filter of claim 32, further comprising: afirst primary external plating terminal disposed on the first primaryexternal electrode; a second primary external plating terminal disposedon the second primary external electrode; a first secondary externalplating terminal disposed on the first secondary external electrode; anda second secondary external plating terminal disposed on the secondexternal electrode.
 34. The common mode filter of claim 31, wherein theprimary coil of each of the at least four coil layers has its primaryexternal terminal and primary internal terminal at both ends thereof,and the secondary coil of each of the at least four coil layers has itssecondary external terminal and secondary internal terminal at both endsthereof.
 35. The common mode filter of claim 34, further comprising: afirst discontinuous part between the second primary external terminalsof two of the at least four coil layers; and a second discontinuous partbetween the second secondary external terminals of two of the at leastfour coil layers.
 36. The common mode filter of claim 34, furthercomprising: a first insulating wall disposed between the primaryexternal terminal of the at least four coil layers and the secondprimary external plating terminal; and a second insulating wall disposedbetween the second secondary external terminal of the at least four coillayers and the third secondary external plating terminal.
 37. The commonmode filter of claim 34, wherein the primary internal terminals of twoof the at least four coil layers are connected with a primary via andthe primary external terminals of another two of the at least four coillayers are connected with each other.
 38. The common mode filter ofclaim 34, wherein the secondary internal terminals of two of the atleast four coil layers are connected with a secondary via and thesecondary external terminals of another two of the at least four coillayers are connected with each other
 39. The common mode filter of claim31, wherein each of the four coil layers includes a dummy primaryexternal electrode and a dummy secondary external electrode that areseparate from the primary coil and the secondary coil.